1. Field of the Invention
This invention relates to digital data communication systems and their method of operation with hierarchical closed cable loops which emanate from and return to a central controller adopted for connection to a central processing unit. More particularly, the invention relates to a hierarchical loop communication system in which the assignment of frames to individual devices is based upon availability of frames and instantaneous demand. Further, this invention relates to such systems in which the hierarchical loops are asynchronous.
2. Description of the Prior Art
U.S. Pat. No. 3,732,543 of Rocher et al. shows a hierarchical loop system in which a definite time slot is allocated to each station, on a rotating basis as a function of demand.
U.S. Pat. No. 3,731,002 of Pierce shows another hierarchical system.
An object of this invention is to provide simultaneous inbound and outbound communication within a loop system without inbound outbound contention for service.
Another object of this invention is to provide a loop to computer interface affording sharing, of access to the memory of the computer.
Another object of the invention is to permit access by devices on the loop to inbound frames upon an unassigned demand basis.